Multiple piston incremental rams

ABSTRACT

A MULTIPLE PISTON INCREMENTAL RAM AS USED FOR MACHINE TOOL POSITIONING OR A DIGITAL TO ANALOGUE CONVERTER IS CHARACTERISED IN THAT THE PISTONS WORK IN AN ARCUATE CHAMBER. THE PISTONS ARE OF S OR Z SHAPE SO THAT THEY HOOK ON ONE ANOTHER IN AN INTERCONNECTED SERIES AND CONVENIENTLY HAVE A CENTRAL PART WHICH SEALS SLIDINGLY ON THE WALLS OF THE CHAMBER. THE CHAMBER CAN BE ANNULAR OR HELICAL AND THE OUTPUT CAN BE VISUAL OR MECHANICAL. ACTUATING PORTS ARE PROVIDED BETWEEN THE VARIOUS CENTRAL PARTS AND A RESETTNG PORT IS ALSO PROVIDED. CONVENIENTLY THE CHAMBER AND PISTONS ARE BOTH OF PLASTIC MATERIAL THE PISTONS BEING FORMED OF A THERMALLY SOFTENING PLASTICS MATERIAL STRIP.

3 Sheets-Sheet 1 Filed June 10, 1969 llii INVENTOR: W490,

' BY M P1 CHAPD Nov. 9, 1971 R. WARD MULTIPLE PISTON INCREMENTAL RAMS 3 Sheets-Sheet 3 Filed June 10, 1969 INVENTOR: W490,

United States Patent 01 ice 3,618,474 Patented Nov. 9, 1971 US. Cl. 92-5 12 Claims ABSTRACT OF THE DISCLOSURE A multiple piston incremental ram as used for machine tool positioning or a digital to analogue converter is characterised in that the pistons Work in an arcuate chamber. The pistons are of S or Z shape so that they hook on one another in an interconnected series and conveniently have a central part which seals slidingly on the walls of the chamber. The chamber can be annular or helical and the output can be visual or mechanical. Actuating ports are provided between the various central parts and a resetting port is also provided. Conveniently the chamber and pistons are both of plastics material the pistons being formed of a thermally softening plastics material strip.

tal incremental ram is known as the PeraDigital Actuator.

One particular application of the invention, which is mentioned merely by way of example, is to a fluidics read-out device by which an output, in numerical quantities in one scale of notation (e.g. the binary scale), is displayed in another scale of notation, e.g. the decimal scale.

In digital svstems the output is often in the form of binary quantities, whereas it is often desirable to display this information in decimal form.

This is commonly carried out in electrical circuits, by uting an electrical binary-to-decimal conversion and using the decimal output to light lamps corresponding to the decimal numbers to be displayed.

A further object of the present invention is to enable a similar technique to be used in fluidics systems, the binary to decimal conversion being carried out fluidically and the output being displayed by mechanical semaphores or the like.

More particularly an object of the invention is to provide a device which will take the output of a fluidic register and convert it directly to decimal read-out form.

The read-out need not necessarily, however, be in the decimal scale but could be in alphabetical, binary or any other form. In the following description, the principle of the invention will, however, be set forth in term of binaryto-decimal conversion and read-out.

Broadly, according to the present invention there is provided a multi-piston incremental ram device wherein the pistons are of arcuate form and work in an arcuate or annular chamber or cylinder.

-In applying the invention to a read-out device in which an output in the form of binary quantities is displayed in decimal form, the final piston of the series may carry numerical information in decimal form on its periphery. This information is appropriately displayed through a window or the like in accordance with the increments of movement made by the final piston of the series. A1-

ternatively the final piston of the series may be caused to operate a device for displaying information in decimal form.

Two particular embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrams.

FIG. 1 is a sectional elevation of one embodiment of the device.

FIG. 2 is a side elevation,

FIG. 3 is a sectional elevation of a second embodiment,

FIG. 4 is a cross-section of FIG. 3, and

FIG. 5 illustrates that both embodiments can be modified to a helical form.

The device shown on the drawings comprises an annular chamber 10 which is conveniently of rectangular rather than circular cross-section and is formed as a groove in a plastics material block 10a closed by a cover 1017. The block and cover are sealed to each other by O-rings. Arranged to work in the cylinder or chamber 10 are a series of interlocking differential stroke, pistons 11, 12, 13 and 14, the piston 14 being the final piston of'the series. These pistons are of a bent S-shape with a central part 23 providing a sliding seal with the walls of the chamber. arcuate lengths 24, and end stops 25 at each end. In the unextended state each central part 23 is abutted on opposite sides by end stops 25 of two adjoining pistons.

The pistons 11, 12, 13 and 14 are arc-shaped so that they will travel around the circular chamber or cylinder 10 when air is admitted to an appropriate port of said chamber as hereinafter described.

The movement or stroke of each piston is limited to a number of binary units represented by the distance between the central part of the piston behind it and an end stop 25 of that piston. For the are x and the movement of the piston 11 by the arc y, the combined movement of these two pistons being x and y.

One end of the cylinder or chamber 10 is provided with a fixed stop 16 which seals between the walls of the chamber at this point and has an end stop 25 for hooking onto the first member.

The chamber is provided with ports 17, 18, 19 and 20. When air is admitted through a port, it enters a region of the chamer bounded by two central parts and pushes them apart until co-operating end stops on the two pistons hook onto each other. These ports are positioned to be between a respective pair of central parts of the pistons. Since the travel of each piston and therefore the distances between a central part and the rearward stop of each piston is greater than the sum of the travels of preceding pistons, it will be seen that the ports will always open out between the same central parts if they are positioned as illustrated.

If air is admitted to the port 17 only, the final piston 14 will be moved around one unit of 12 in 'the particular example shown on the drawing. If air is admitted to the port 18 only, the final piston will be moved two units, i.e. 24. If air is admitted to ports 17 and 18 together then the final piston will be moved three units, i.e. 36.

The ports and associated connectors can be provided in the block 10a or in the cover.

The total arc of travel, of the final piston 14, is limited, in this particular example, to ten units of movement as the device is designed as a binary-to-decimal read-out device for use with a scale-of-ten binary fiuidic register.

The final piston 14 and hence all the other pistons, are biassed to an unextended condition by admitting air to a further port 21 at a lower pressure than that admitted to ports 17 to 20. In some cases where the device is to store a signal, air will only be admitted to port 21 when it is desired to reset the device.

A read-out is obtained from the position of the final piston 14 by engraving on the periphery of said piston indicia 27 such as the numerals and 1 to 9, said numerals being spaced apart by 12 around the final piston. These numbers align appropriately with the window 22 in the circular chamber or cylinder 10 so that they may be observed when the corresponding binary code fluidic signal or impulse is fed to the ports 17, 18, 19 and 20.

The circular chamber and the pistons may be made of transparent material and the numerals made opaque so that a lamp placed, in the centre of the device, will illuminate the numeral being displayed.

The embodiment of FIG. 3 is a very similar except that the pistons 11' to 14' are of curved E shape with the horizontals of adjoining Es directed inward on one piston and outward on the next. Additionally the central parts 23 and the stop 16 are provided with rubber or other piston seals 23a.

The pistons may be of a plastics material strip which is softened by heat and formed into the required shape.

In the embodiment of FIG. 3 the central part can be formed by bending a strip back on itself and cementing or otherwise bonding it integrally.

If a larger display is required an alternative method of display is to mount a drum or disc 51, with the numerals printed on its periphery, close to the chamber and to pivot it at the centre of the chamber. A magnet 52 is placed on the final piston 14 and an armature 53, either of iron or another magnet is fixed to the drum or disc. Thus, the drum or disc will turn to a position dictated by that of the final piston and the readout may be viewed through a suitable window.

A further alternative is to make the chamber 10 helical (FIG. rather than truly circular. The final piston is equipped with a rod 54 projecting from the end of the chamber and this rod can be made to turn a disc, bearing the numerals, coupled to it mechanically. The rod may be used to couple a return spring 55 to the final piston so making it unnecessary to put air pressure on port 21 to bias the pistons.

A helical chamber may also be used to obtain a much longer scale on a device, with the readout system as above described, without making the chamber of an inconvenient diameter especially when more than four binary stages are required, e.g. an alphabetic or multidecade readout.

As the device is basically a fluid binary-to-angular analogue converter the output need not be a visual readout but could be derived from a potentiometer driven or adjusted by the final piston 14 thus giving a fiuid binary to an electrical analogue conversion. Alternatively the output could be derived from a switch or valve thus giving a decimal electrical or decimal fluid output.

In FIG. 4, a block 56 (in chain dot lines) illustrates the potentiometer, switch or valve.

I claim:

1. A multi-piston incremental ram device comprising a housing having internal walls defining an arcuate chamber and interconnected pistons of arcuate form slidable in said chamber, the pistons being interconnected by lostmotion means and defining between them spaces which are expansible to limits imposed by the lost-motion means and the pistons having regions slidably sealed to the walls of the chamber, wherein the lost-motion means between each piston and the preceding piston is capable of at least as much lost motion as the sum of the lost motions of the preceding lost-motion means and wherein each of the pistons except an end one has a central part sealed by a sliding seal to the walls of the chamber to act as a said region and end stops one on each side of the central part for abutment either with the central part or a cooperating end stop of a neighbouring piston whereby to act as the lost-motion means.

2. A device as claimed in claim 1 wherein the pistons having a said central part are of bent S-shape.

3. A device as claimed in claim 1 wherein the pistons having a said central part are of curved E shape with the -Es alternately outwardly and inwardly facing.

4. A device according to claim 1 wherein associated with each piston there is a port in the chamber adjacent a sealing region of the piston but disposed so that despite movement of the piston and all preceding pistons it remains on the same side of that pistons sealing region.

5. A device according to claim 1 wherein the chamber has a rectangular cross-section.

6. A device according to claim 1 wherein the final piston of a series bears indicia which are visible through a window in the chamber whereby the device can be used as a binary signal to decimal or other signal converting device.

7. A device according to claim 1 wherein the final piston of a series is magnetically coupled to a display means.

8. A device according to claim 1 wherein the chamber is helical rather than circular and the final piston of a series has a projecting rod which is coupled to a display means.

9. A device according to claim 8 wherein the rod is associated with a return spring for resetting the device.

10. A device according to claim 1 wherein there is provided a port to reset the device.

11. A device according to claim 1 wherein the housing is of plastics material.

12. A device according to claim 1 wherein the pistons are of plastics material.

References Cited UNITED STATES PATENTS 2,197,867 4/1940 Klement 91167 A 2,437,552 3/1948 QuirOZ 92-5 2,911,956 11/1959 Smith, Jr. 91-167 A 3,289,544 12/1966 Daniels 91167 A PAUL E. MASLOUSKY, Primary Examiner U.S. c1. X.R. 

